It is known that numerous modular joint prosthesis systems from various manufacturers are in use which result in problems in selecting the correct prosthetic component during the surgical procedure, in particular for the replacement of damaged or worn components of a joint prosthesis, such as ball joints or adapters. Frequently, this is because the manufacturer has discontinued production of the joint prosthesis in question, or the manufacturer is no longer active in the market. During the procedure, the surgeon must quickly decide whether an adapter or a ball joint from a different manufacturer is compatible with the outer cone of the prosthesis shaft which is inserted into the femur, or whether a completely new modular joint prosthesis system must be inserted.
The latter course of action prolongs the procedure for the patient, which is already relatively lengthy, and is often associated with separation of the femur (U.S. Pat. No. 5,100,407 A). In addition, the selection of an adapter which fits on the outer cone of the femoral prosthesis shaft from a set of adapters, using the trial and error method, is time-consuming, and is ultimately unsatisfactory for the patient (EP 0 767 638 B1).
Furthermore, a test instrument is known from DE 103 29 241 A1 for assessing the cone seat of hip endoprostheses, using a test film which allows the bearing area ratio of a cone seat to be determined.